This invention relates to deep oil cooking apparatus and particularly to such apparatus for rapid and efficient cooking of chicken, other meat products, vegetables and food products.
Generally a restaurant menu often includes chicken, fish, vegetables and other foods which may be cooked or fried by immersion in hot cooking oil. Certain restaurants specialize in such foods, particularly deep cooked chicken. In addition to the conventional restaurant where the food is consumed on the premises, various restaurants and other food retail outlets have a substantial food carry-out business including chicken. In those restaurants and other outlets having large sales volume of cooked foods, a rapid and efficient cooker is essential in order to produce quality products at a reasonable and profitable cost.
The conventional apparatus for deep cooking includes a relatively large kettle or pot having a releasable high pressure sealed cover. The pot is filled with cooking oil to a level in spaced relation to the cover. A heating unit generally in the form of immersion heating elements or an encircling heat unit applied adjacent to the pot is operative to increase the temperature of the oil to the desired cooking level. With the external heating unit, the heating unit may be held abutting the pot or spaced from the pot to establish heating by radiant energy. The chicken is placed in a suitable multiple shelf basket for transfer and immersion into the cooking oil for deep cooking for a selected period and removable therefrom. For example, a widely used cooker includes a rectangular shaped pot of approximately 13-17 inches across and a similar depth. The cooker is adapted to maintain and cook approximately ten pounds of chicken parts in each cycle. In one system, the oil is raised to a temperature of 370.degree. to 375.degree. and the power is cutoff just prior to placing the chicken in the pot. The chicken is then cooked for approximately eleven minutes and removed. Other commercial production units are constructed to operate with a continuous power supply and with the oil held at a temperature of about 350.degree. F. to prevent boiling of the oil.
In all systems, a valve unit is provided for periodic withdrawal and replacement of the oil from the cooking apparatus. Systems for filtering of foreign material from the oil which is created during the cooking process have also been suggested. Thus, a consistent and flavorable product is dependent upon use of clean oil which has not been burnt or otherwise broken down. Although such systems are widely used, the present inventor has recognized a number of features which contribute to inefficiency of the cooking apparatus, as well as unnecessary costs.
The oil is held at the high temperature and the temperature in the cooker above the oil level tends to rise to a level which may cause scorching of the oil. The oil of course is contaminated with foreign matter during the cooking sequence and in general practice a batch of oil is withdrawn and periodically replaced with fresh oil, which may have been preheated. The replacement of the oil combined with the necessity of heating the oil reduces the efficiency of system operation.
Prior art commercial units have generally used immersion heating elements projecting into the oil within the lower end of the cooking pot. The immersion heating elements are operated at approximately 350.degree. Fahrenheit. The temperature at which oil will boil is approximately 360.degree. Fahrenheit and the immersion units are operated as close to such temperature as possible without significant possibility of boiling. Immersion units are known to have certain distinct disadvantages. Operation at such high temperatures is used to rapidly heat the oil results. However, some scorching of the oil results with a degradation of the oil. Generally for every 20.degree. of increase in temperature above 300.degree. for example, the degrading effect is approximately doubled. The degradation of the oil at least in part is created each time the cooking pot is opened because the oil is at the high temperature and the oil surface is agitated. In addition, when cooking breaded products such as deep fried or cooked chicken, some of the breaded coating, which is widely applied to the uncooked chicken, drops from the chicken during the cooking process. The crumbs and even small pieces of chicken fall through the oil to the bottom of the pot, and in so moving some is often deposited on the heating elements. The coating on the heating elements not only reduces the heat input into the oil but results in increased scorching of the oil as the result of the excessive frying of the breading product. Generally this requires frequent discarding of the oil and replacing of the oil with totally clean new oil.
The cooking oil is a significant cost factor of commercial production of deep cooked food and operators are continuously monitoring and taken such action as possible to minimize oil usage. This may result in using of oil which is marginally acceptable and compromising with a somewhat lesser quality product. This is particularly true in operations which may be operated by managers rather than owners of the commercial operation.
Although exterior encircling heating units have been suggested including radiant heating units to avoid the difficulties associated with immersion units, the provision of an adequate external heating unit which rapidly heats the oil to the operating temperatures and maintains the oil at the desired temperature have not been to the inventor's knowledge satisfactorily solved. The cooking pot within which the product is placed is generally a relatively large flat, wide pot having a depth approximately equal to the width, with the product uniformly distributed throughout the cooking oil. The cooking oil is a relatively poor conductor of heat and consequently with external heaters it has been difficult to produce the desired heating level within the oil particularly with a highly uniform temperature through the oil proper.
The cost of the oil in the prior art devices is particularly significant because of substantial quantities of oil used to cook products and the associated relatively high energy levels required to heat the oil. Generally, in commercial production 55 to 60 pounds of oil are used for batch cooking of 10 pounds of product. Total replacement with fresh oil results in a significant cost factor. A large heating units operating to produce 11 to 12 kilowatts of energy are necessary to produce the proper temperature and time cycle. The heating units are distributed over the large surface of the oil to minimize the wattage per square inch of surface and thereby minimize scorching of the oil. Because of the relatively large flat pots required by the large oil level quantities, both the oil cost and the energy costs are extremely significant.
The high pressure cooking process also requires release of the pressure within the cooker prior to complete removal of the cover. However, the system should permit the rapid cycling and the removable of the cooked chicken and replacement with a fresh batch of uncooked chicken. The cover is therefore generally provided with a mechanical latch mechanism which incorporates a pressure release mechanism. The efficiency of the cycling is directed related to the efficiency of the mechanical release mechanism.
Although various deep cooking pot units are used in the industry, there is a continuing need for a more efficient and effective batch cooking pot-type apparatus and particularly an apparatus which provides for a more rapid and energy efficient cooking cycle.